Gliomas are malignant tumors accounting for about 60% of primary brain tumors, have high incidence and are difficult to treat. Thus, effective treatment methods other than radiotherapy for gliomas have not yet reported. Among gliomas, glioblastoma (GBM) classified as the most malignant form has a very high resistance to radiotherapy and chemotherapy compared to other cancers, and thus life expectancy after diagnosis of glioblastoma is only one year. However, in the case of such brain tumors, the delivery of therapeutic drugs is not easy due to the presence of blood-brain barriers. Particularly, because of the insufficient understanding of brain neurobiology, the development of therapeutic agents is slowly progressing. Further, glioblastoma represents an aggressive variant compared to other brain tumors, and thus can cause lethal results within several weeks, if it is not treated within a short time. Treatment of glioblastoma is performed by radiotherapy and chemotherapy in addition to surgical therapy. However, because chemotherapy has reached its limit due to the occurrence of resistant variants, recurrence caused by tumor stem cells, etc, there is a need to develop new therapy.
In recent years, with the rapid development of systems biology and bioinformatics tools, genetic defects and gene expression patterns, which are considered to be associated with the development and progression of glioblastoma, have been reported. However, the screening of molecular markers that can represent clinical results is still insufficient. Particularly, gene expression analysis is performed at the transcriptome level, and thus cannot indicate the expression level of protein in actual cancer tissue. As a solution to this problem, the use of an animal model that best mimics glioblastoma has been proposed. This animal model can be used to study the development and progress of glioblastoma. Moreover, it can be used for the investigation of a new therapeutic strategy for glioblastoma and studies on a suitable combination of existing therapeutic strategies. In addition, it is expected to be used to examine the effects of new antitumor substances showing therapeutic effects against glioblastoma.
Accordingly, immune-compromised model animals such as nude mice have been used, or studies have been actively conducted to develop a glioblastoma-induced animal model. For example, the production of an animal model by transplantation of human glioblastoma was reported (Diao Yi, et al., Cancer Investigation, 29:229-239, 2011, EGFR Gene Overexpression Retained in an Invasive Xenograft Model by Solid Orthotopic Transplantation of Human Glioblastoma Multiforme Into Nude Mice). In the above paper, a mouse model was produced using only a graft sample prepared from the piece of a specific portion (single portion) of patient-derived glioblastoma, and thus there was difficulty in producing a glioblastoma mouse model showing the same genetic, morphological and pathological characteristics as those of the parental tumor. In addition, in a process for preparing a sample for preparing a graft sample for transplantation into a mouse according to the prior art, protease was used for enzymatic degradation of a tissue collected from a patient, but in this case, there is difficulty in separating the tissue into single cells, due to the viscosity of the tissue. Moreover, the Ficoll gradient method was generally used to remove erythrocytes from a graft sample collected from a patient, but in this case, there was a problem in that the efficiency with which blood is removed is low.
In order to treat a glioblastoma patient, the genetic, physiological and environmental characteristics of the patient should be taken into consideration, and various therapies, including chemotherapy, radiotherapy and surgical therapy, should be applied depending on the degree of progression of glioblastoma. However, because the above-described animal model cannot reflect the individual characteristics of a glioblastoma patient, it is merely used for the development of therapeutic methods or agents, and the actual use thereof for patient-specific treatment was limited. It is expected that, if an animal model that can best mimic the genetic and physiological conditions of each patient, the success rate of treatment can be greatly increased by performing a treatment specific for each patient.
Under such circumstances, the present inventors have made extensive efforts to establish a glioblastoma mouse model showing the same genetic, morphological and pathological characteristics as those of a glioblastoma patient, and as a result, have found that, when a graft sample, prepared from a mixture of glioblastoma tissue pieces, collected from various portions of glioblastoma tissue isolated from a glioblastoma patient, is orthotopically transplanted into the brain of a mouse, a glioblastoma mouse model showing the same genetic, morphological and pathological characteristics as those of the parental tumor can be established. In addition, the present inventors have developed the optimum conditions for establishing this mouse model, thereby completing the present invention.